Whether it's a cooking, automotive or lubricating oil mark, the sooner you deal with a greasy stain, the better the outcome. Apply an absorbent such as talcum powder or cornstarch to the affected area, then brush away.
Place stain facedown on paper towels.
Blot back of stain with a dry-cleaning solvent. Replace paper towels as they soak up the stain. Spray with laundry pretreatment. Wash in the hottest water that's safe for the garment. Inc. How things get done.