Melt the 2 Tbsp butter in a medium microwave-safe dish.
Add in the ¼ cup oats, ¼ cup flour, and 1 Tbsp sugar and use a fork to mix together until it holds together in clumps.
Top each ramekin with half the crumble mixture.
Place both ramekins on a parchment-paper lined baking sheet (if they're stuffed full they may bubble over), and bake 30 minutes.
Remove from the oven and allow to cool for 10-15 minutes before serving. Top with ice cream or other garnishes (chocolate sauce, sprinkles, etc.) if desired.