A frame for a tracked skid steer loader machine or multi-terrain loader machine is provided having a structural design that enables the loader machine to be modularly assembled using a variety of pre-assembled components, namely a lower frame assembly, an upper frame assembly and an undercarriage. The lower frame assembly includes a pair of recessed channels formed on a base portion of the lower frame assembly and extending the width of the lower frame assembly. The undercarriage includes right and left track assemblies connected by a pair of crossmembers. Each recessed channel is engagingly associated with a respective crossmember of the undercarriage, thereby allowing for the modular assembly of a loader machine when the recessed channels of the lower frame assembly are mounted over the crossmembers of the undercarriage. An upper frame assembly may be mounted on the lower frame assembly before or after the lower frame assembly is mounted onto the undercarriage.