Preheat the oven to 350°F. Combine the butter, light brown sugar, and white sugar in a large bowl and beat with an electric mixer until smooth.
Add the eggs, vanilla, syrup, and baking soda. Mix to combine. Mix in the peanut butter and then the oats.
Add the chocolate chips, mixing them in thoroughly. Use a cookie scoop (I like this one!) to portion the dough onto baking sheets. Top each cookie dough mound with M&Ms.
Bake for approximately 12 minutes, watching carefully to make sure they do not overbake. The cookies should be barely browned around the edges and just past looking wet on top. Cool on sheet for 1 minute and then remove to wire rack.