OK, so the story is that I got this recipe from a co-worker about 20 years ago. I made a batch to take to a family function and the niece and nephews (and my brother) fell in love with them. They asked me what they were called and I said “Chocolate Rebel Bars,” but they (being little kids at the time) didn’t understand what I said and called them “Rubber Bars.” The name stuck and we still call them Rubber Bars!
Cream together 2 sticks of butter and the brown sugar; add eggs and vanilla. Beat with a mixer until incorporated.
Add the flour and baking soda; mix to combine.
Add the oatmeal, mix to incorporate. I like to use my hands like I would to mix meatloaf. If you have a heavy-duty hand mixer or a stand mixer you can use them instead.
Spread 2/3 of the oatmeal mixture into a buttered 13x9 baking pan. Press it in and smooth the top.
In a glass or ceramic bowl (microwave-safe) combine the bag of milk chocolate chips, sweetened condensed milk, vanilla and butter. Microwave for 30 seconds, stir, microwave for another 30 seconds; stir to combine and finish melting.
Pour the chocolate over the oatmeal mixture in the pan and spread evenly. Try to keep it just back from the sides of the pan -- it will burn while baking.
Crumble the remaining 1/3 of the oatmeal mixture unevenly over the chocolate.
Bake at 350 degrees for 25-30 minutes. If using a glass baking dish, lower your temp to 325 degrees and check after 25 minutes. The top should be light golden brown; the edges should not be darker than the middle. It's OK to take it out a little on the under-done side.
Let cool to room temperature before trying to cut. I like to refrigerate mine overnight. The next morning the whole thing pops out of the pan and I can cut it into any size bars I want. I usually cut into about 1 1/2 x 1 1/2 inches.
This is also good right out of the oven with vanilla ice cream on top melting all over...MMMMmmm!