On a year-over-year basis, we grew our top-line net sales by 34%, expanded gross margins 590 basis points, and increased operating income by 237%.
While we have undoubtedly been active via acquisitions in the last four-plus years, fiscal-year 2021 quarter 2 represents a truly organic year-over-year comparison in total performance.
As a result, our consolidated second-quarter gross margin of 18.6% represents an increase of 590 basis points versus last year.
Quarter 2 lost net sales due to sourcing constraints was easily eight figures across the portfolio.
That revenue opportunity remains inherent in our potential as we transition into quarter 3.
In the next three months of 2021, March through May, which is our quarter 3, we'll see strong retail and wholesale comparisons versus a period of intense marketplace disruption a year ago.
Second-quarter consolidated revenues were a record $839.9 million, which is an increase of 34% compared to $626.8 million for the fiscal 2020 period driven, as Mike noted, by strong consumer demand for Winnebago Industries' great brands.
As a reminder, 100% of Newmar is reported in the result of our Motorhome segment.
Gross profit margin increased 590 basis points to 18.6%, while adjusted EBITDA margin increased 570 basis points to 12.9% compared to 7.2% for the fiscal 2020 period.
Similar to our fiscal 2021 Q1 performance, this significant margin expansion was driven by favorable pricing, including lower discounts and allowances; productivity initiatives; operating leverage approximating 200 to 250 basis points, and segment mix.
Reported earnings per diluted share were a record $2.04 compared to reported earnings per diluted share of $0.51 in the same period last year.
Adjusted earnings per diluted share were likewise a record at $2.12 in the second quarter for an increase of 216% compared to the same quarter in fiscal 2020.
Adjusted EBITDA was $108 million for the quarter, compared to $45.4 million last year, which is an increase of 138%.
Revenues for the Towable segment were $439.3 million for the second quarter, up 55% over the prior year, driven by elevated consumer demand across the Towables portfolio.
Winnebago Industries unit share of the North American towable market continues to grow as share on a trailing three-month basis through January 2021 was 12.4% or an increase of 80 basis points over the same period last year.
Segment adjusted EBITDA was $62.4 million, up 79.5% over the prior-year period.
Adjusted EBITDA margin of 14.2% increased 190 basis points primarily due to favorable pricing and operating leverage.
In the second quarter, revenues for the Motorhome segment were $382.6 million, up 17.5% from the prior year, driven by increased unit sales in our Class B and Class C products.
Compared to the same period last year, second-quarter Class C unit sales were up 24.5%, while Class B products were up a very robust 81%.
Class B market share continues to be strong, as evidenced by our rolling three-month retail unit market share of 45.7% through January of 2021.
Segment adjusted EBITDA was $51 million, up 241% from the prior year.
Adjusted EBITDA margin increased 870 basis points over the prior year to 13.3%, driven by our ongoing focus on operational efficiency, including the transition to a build to dealer order business model in the Winnebago-branded Motorhome business, as well as several other operating improvements and lean initiatives that our business have pursued over the past several years, in addition to pricing actions to ensure our pricing is commensurate with market dynamics and also operating leverage.
As we have stated previously, we continue to expect to achieve a level of sustained profitability that is notably above the 4% to 5% EBITDA yield we've delivered in this segment for the past several years.
Continuing the trend from Q1, our leverage ratio, net debt-to-adjusted EBITDA continued to decline and is now 1.0 times, which is toward the lower end of our targeted range of 0.9 to 1.5 times, driven by both strong EBITDA generation and lower net debt due to the increasing cash balance of now $333 million.
Total liquidity, including our untapped ABL, is now in excess of $500 million.
Cash flow from operations was a healthy $66.9 million for the first half of fiscal 2021.
Our effective tax rate increased to 23.4% for the first six months ended February 27, 2021, from 20.1% for the same period last year primarily due to consistent year-over-year credits over higher current-year pre-tax income and favorable R&D discrete items in fiscal 2020.
For the full year, we currently expect our tax rate to approximate 23.5% to 24%, including all discrete -- or I'm sorry, excluding all discrete items from year-to-date results, and those that may occur in the remainder of the year.
During the second quarter, we paid a dividend of $0.12 per share on January 27, 2021, and our board of directors just approved a quarterly cash dividend of $0.12 per share payable on April 27, 2021.
In our fiscal 2021, which is September of 2020 through August of 2021, we believe RV industry retail will grow in the mid- to upper single digits, while industry wholesale shipments in that same period will grow approximately 40% to 45%.
Quarter 3, March through May for our company, industry retail should be especially strong given the comparisons versus 2020.
But quarter 4 for our organization, June through August, industry retail will see a more challenging comparison environment due to record-breaking bounce-back RV retail last summer.
Please note that our fiscal industry wholesale shipment projection considers and aligns with the RV Industry Association calendar year 2021 industry midpoint forecast of approximately 533,000 units, or plus 24%, a forecast which we support.
Our most recent field inventory reports early here in quarter 3, continue to show low field inventory levels in Winnebago Industries' RV and marine businesses.
Depending on the brand or the product category, field inventory is anywhere between 20% lower than a year ago to 60% lower.

Summary:
Second-quarter consolidated revenues were a record $839.9 million, which is an increase of 34% compared to $626.8 million for the fiscal 2020 period driven, as Mike noted, by strong consumer demand for Winnebago Industries' great brands.
Reported earnings per diluted share were a record $2.04 compared to reported earnings per diluted share of $0.51 in the same period last year.
Adjusted earnings per diluted share were likewise a record at $2.12 in the second quarter for an increase of 216% compared to the same quarter in fiscal 2020.