Process to make ethylene and propylene, in a combined XTO-OC process, from an oxygen-containing organic feedstock being methanol, dimethylether or mixture thereof comprising: a0) providing a first portion and a second portion of said oxygen-containing organic feedstock a) providing a catalyst comprising zeolitic molecular sieves containing a 10 membered ring pore openings in their microporous structure, b) providing an XTO reaction zone using a fluidized bed reactor, an OC reaction zone using a fluidized bed reactor and a catalyst regeneration zone using a fast fluidized bed system, said catalyst circulating in the three zones,; c) contacting the first portion of said oxygen-containing organic feedstock in the XTO reactor with the catalyst at conditions effective to convert at least a portion of the feedstock to form a XTO reactor effluent comprising ethylene and propylene and a hydrocarbon fraction containing C4-C7 olefins; d) separating said ethylene and propylene from said hydrocarbon fraction containing C4-C7 olefins; e) contacting said hydrocarbon fraction containing C4-C7 olefins and the second portion of said oxygen-containing organic feedstock in the OC reactor with the catalyst at an inlet temperature of 400 to 650°C, a LHSV ranging from 0.5 to 30 hr -1, an olefin partial pressure of 10kPa to 200 kPa (0.1 to 2 bars) to convert at least a portion of said hydrocarbon fraction containing C4-C7 olefins and oxygen-containing organic feedstock to ethylene and propylene; wherein all the catalyst from the regenerator is sent to the OC reaction zone, then further sent to the XTO reaction zone and finally part of the catalyst of the XTO reaction zone is sent to the regenerator, the regeneration zone, and the other part is sent to the OC reaction zone and wherein the OC reactor effluent and the XTO reactor effluent are mixed and sent to a fractionator, or sent to the same fractionator, and the ethylene and propylene are recovered; at least a portion of the hydrocarbon fraction containing C4-C7 olefins are recycled at the inlet of the OC reactor; and wherein before recycling said hydrocarbon fraction containing C4-C7 olefins at the inlet of the OC reactor, said hydrocarbon fraction containing C4-C7 olefins are sent to a second fractionator to purge the heavies and wherein the zeolitic molecular sieve provided in a) is an alkaline earth or rare earth metal P-modified molecular sieve. M-P-modified molecular sieve, wherein the P-content in the M-P-modified molecular sieve is at least 0.3 wt%. the amount of alkaline earth or rare earth metal in the M-P-modified molecular sieve is at least 0.05 wt%, the molar ratio of M/P in the M-P-modified molecular sieve is less than 1. wherein the M-P-modified molecular sieve is made by a process comprising the following steps: a) selecting a P-modified molecular sieve which contains at least 0.3 wt% of P. wherein the molecular sieve is an aluminosilicate of the MFI structure: b) contacting the P-modified molecular sieve selected in a) with a solution of an alkaline earth or rare earth metal-containing compound, M-containing compound, to introduce at least 0.05 wt% of the alkaline earth or rare earth metal-containing compound: and wherein the process further comprises the following steps, in the order given: - separation of the solid from the liquid; - an optional washing step or an optional drying step followed by a washing step: - a calcination step. a0) providing a first portion and a second portion of said oxygen-containing organic feedstock a) providing a catalyst comprising zeolitic molecular sieves containing a 10 membered ring pore openings in their microporous structure, b) providing an XTO reaction zone using a fluidized bed reactor, an OC reaction zone using a fluidized bed reactor and a catalyst regeneration zone using a fast fluidized bed system, said catalyst circulating in the three zones,; c) contacting the first portion of said oxygen-containing organic feedstock in the XTO reactor with the catalyst at conditions effective to convert at least a portion of the feedstock to form a XTO reactor effluent comprising ethylene and propylene and a hydrocarbon fraction containing C4-C7 olefins; d) separating said ethylene and propylene from said hydrocarbon fraction containing C4-C7 olefins; e) contacting said hydrocarbon fraction containing C4-C7 olefins and the second portion of said oxygen-containing organic feedstock in the OC reactor with the catalyst at an inlet temperature of 400 to 650°C, a LHSV ranging from 0.5 to 30 hr -1, an olefin partial pressure of 10kPa to 200 kPa (0.1 to 2 bars) to convert at least a portion of said hydrocarbon fraction containing C4-C7 olefins and oxygen-containing organic feedstock to ethylene and propylene; a) selecting a P-modified molecular sieve which contains at least 0.3 wt% of P. wherein the molecular sieve is an aluminosilicate of the MFI structure: b) contacting the P-modified molecular sieve selected in a) with a solution of an alkaline earth or rare earth metal-containing compound, M-containing compound, to introduce at least 0.05 wt% of the alkaline earth or rare earth metal-containing compound: and wherein the process further comprises the following steps, in the order given: - separation of the solid from the liquid; - an optional washing step or an optional drying step followed by a washing step: - a calcination step. - separation of the solid from the liquid; - an optional washing step or an optional drying step followed by a washing step: - a calcination step.